Method of maintaining uniformity of fibrous material fed to a continuous digester

Abstract

A process for continuously monitoring and controlling a continuous process for digestion of cellulose utilizing a computer which is programmed to determine (1) the mass of wood being fed to the digester from measurements of the density of the wood slurry feed, the density of the liquid and the total flow of slurry, (2) the mass of wood being withdrawn from the digester from measurements of the density of the pulp slurry, the density of the liquor and the total flow of slurry, (3) the correct amount of fresh digester liquor to be added concurrently with the wood feed and (4) amount of water wash and makeup digester liquor to be fed to the reactor. The computer can also be programmed to control the temperature in the reaction zone of the digester.

What is claimed is: 
     
       1. A method of maintaining uniformity of the amount of cellulosic fibrous material fed to a continuous pulp digester in a feeding process in which the material is continuously introduced into a liquid to form a liquid-material slurry which is continuously conveyed to the inlet end of the continuous digester where the material is continuously separated from the main body of the liquid and continuously deposited into the digester inlet while the separated liquid is continuously recirculated to form a part of the slurry, said method comprising the steps of continuously measuring the gamma radiation absorption of the slurry so as to derive continuous measurements which are a function of any continuous variations in the combined densities of the material and the liquid of the slurry resulting from (1) continuous variations in the amount of material in the slurry alone, or (2) continuous variations in the density of liquid portion thereof alone, or (3) continuous variations in both (1) and (2);   continuously measuring the total flow of the slurry;   continuously measuring the gamma radiation absorption of the recirculated liquid so as to derive continuous measurements which are a function of any continuous variation in the density of the liquid of the slurry;   utilizing the continuous gamma radiation absorption measurements of the recirculated liquid and the flow measurement of the slurry to compensate for variations in the continuous gamma radiation absorption measurements of the slurry resulting from variations in the density of the liquid of the slurry to thereby obtain a continuous indication of any variation in the amount of material in the slurry; and   utilizing the continuous indication of any variation in the amount of material in the slurry to change the amount of material in the slurry in a manner tending to make the amount of material in the slurry uniform.